1. Field of the Invention
The present invention relates to a rotary head type magnetic recording/playback apparatus (hereinafter referred to as a VTR) in which a magnetic tape is wound around a cylindrical rotary head cylinder, having a rotary head built therein, to record/playback a signal by the rotary head. In particular, this invention relates to a loading post driving device for automatically withdrawing a magnetic tape out of a tape cassette having a supply reel and a take-up reel provided therein, and winding the tape around the rotary head cylinder over a predetermined circumferential angle range.
2. Prior Art
Recently, various attempts have been made to reduce the size, weight and height of VTRs. In particular, because the mechanism for loading a magnetic tape in the VTRs has a very complicated arrangement, requires a large number of parts, and considerably affects the size of the VTR as a whole, improving development of the loading mechanism has become a quite important theme.
A conventional loading mechanism will be described below with reference to the drawings. FIG. 15 is a top plan view of a loading post driving device in the prior art. In the drawing, denoted by reference numeral 1 is a tape cassette provided in the front surface thereof with recessed portions 2 and 3 which are disposed in such a manner that a loading post 4 at the supply side (a loading post of the supply side) and an inclined post 5, both mounted on a boat (a movable carrier) 8 at the supply side (a boat of the supply side), are relatively inserted into the recess 2, and a loading post 6 at the take-up side (a loading post of the take-up side) and a tape post 7, both mounted on a boat (a movable carrier) 9 at the take-up side (a take-up side boat 9), are relatively inserted into the recess 3, respectively. The supply side boat 8 and the take-up side boat 9 are connected with a ring 12 at the supply side and a ring 13 at the take-up side, respectively, through relay links 10 and 11 so that, as the rings 12 and 13 rotate, the boats 8 and 9 are guided along a loading guide shot 14 at the supply side and a loading guide slot 15 at the take-up side, respectively. Thereby, a magnetic tape (not shown) is withdrawn from the tape cassette 1 and wound around a rotary head cylinder (not shown).
As shown in FIG. 16, the take-up side boat 9 has a shaft 9a and the shaft 9a extends through the guide slot 15 of a loading guide plate 15a at the take-up side. The supply side boat 8 also engages with the loading guide slot 14 of another loading guide plate in a similar manner.
However, the above conventional arrangement has suffered from such a first problem that the guide plates are necessarily required to retain the boats 8 and 9 in the guide slots 14 and 15, respectively, thus causing limitations in reduction of the area occupied by the loading mechanism and preventing miniaturization of VTRs.
In view of the above, it has also been considered to use loading guide rails instead of conventional guide slots. More specifically, as shown in FIG. 17, an arm 13a extending from a ring 13' of the take-up side is connected with a boat 9' of the take-up side through an engagement portion 13b so that, as the take-up side ring 13' rotates, the take-up side boat 9' is guided along a loading guide rail 15' of the take-up side.
In addition, as shown in FIG. 18, the loading guide rail 15' of the take-up side is provide along the outer circumference thereof with a T-section rail portion 15a projecting upwardly and downwardly at the peripheral edge. The take-up side boat 9' is provided with a hook projection 9a arranged to engage the T-section portion 15a. The take-up side boat 9' is securely held on the T-section portion 15a to be guided along the loading guide rail 15' of the take-up side with rotating of the take-up side ring 13'.
Note that a loading mechanism at the supply side is also arranged in a similar manner and thus will not be explained herein.
According to the above known arrangement, however, because the take-up side boat 9' is only held through the engagement between the T-section portion 15a and the hook projection 9a, ensuring secure holding of the take-up side boat 9' requires extending the amount which the portion 15a projects vertically and increasing the extent which the T-section portion 15a engages with the hook projection 9a, the leading to difficulties in reducing a height of the loading mechanism.
Next, a loading post driving device previously proposed by the present inventors in Japanese Patent Application No. 2-260796 as an art of reducing the size and weight of a magnetic recording/playback apparatus will be described with reference to the drawings.
FIG. 19 is a schematic top plan view of the loading post driving device and FIG. 20 is a perspective view showing principal parts of the loading post driving device. Note that rotary head cylinder 69 is omitted in FIG. 20 for brevity of the drawing and convenience of the description.
In FIG. 19, 51 denotes a chassis and 52 a tape cassette charged on the chassis 51. A supply reel 53 and a take-up reel 54 are provided in the tape cassette 52. When the tape cassette 52 is charged on the chassis 51, a loading roller post 58 of the supply side and a tension post 59; first and second loading roller posts 60 and 61 of the take-up side; and a pinch roller 62 are positioned inside of a magnetic tape 63 and in recesses 55, 56 and 57 formed on the front edge surface of the tape cassette 52, respectively. Denoted by 64 and 65 are the supply side boat and a take-up side boat on which the loading roller post 58 of the supply side and the first and second loading roller posts 60 and 61 of the take-up side are mounted, respectively. The supply side boat 64 is also provided with an inclined post 66, in addition to the loading roller post 58 of the supply side, the inclined post 66 existing within the recess 55 together with the loading roller post 58 of the supply side. Denoted by 67 and 68 are an arc shape loading guide of the supply side and another arc shape loading guide of the take-up side disposed along the circumference of a rotary head cylinder 69 as shown in FIG. 20. The guides 67 and 68 operate to guide the supply side boat 64 and the take-up side boat 65 during the operation of loading the magnetic tape 63, respectively. Also as shown in FIG. 20, the supply side loading guide 67 is arranged such that an end side of the guide 67 along which the boat 64 returnably moves is raised higher than a proximate end side of the guide 67 which is a home position of the boat 64. On the other hand, the take-up side loading guide 68 is arranged such that an end side of the guide 68 along which the boat 65 returnably moves is lowered than a proximate end side of the guide 68 which is a home position of the boat 65.
The supply side boat 64 is driven by a ring 85 of the supply side having an arm 86 on which a distal end portion of drive shaft 76 of the supply side is mounted. As will be seen from FIG. 20, the supply side boat 64 is arranged to be vertically movable along the drive shaft 76 through a hole 78 of the boat 64. The rotary head cylinder 69 is attached substantially vertically with respect to the chassis 51. When the supply side boat 64 is moved along the supply side loading guide 67, the supply side loading roller post 58 winds the magnetic tape 63, withdrawn out of the supply reel 53, around the rotary head cylinder 69 in a direction extending obliquely upwards along a left side surface area of the cylinder 69. When the take-up side boat 65 is moved along the take-up side loading guide 68, the take-up side loading roller post 60 winds the magnetic tape 63 withdrawn out of the take-up reel 54 around the rotary head cylinder 69 in a direction extending obliquely downwards along a right side surface area of the cylinder 69.
Denoted by 70 is a capstan provided on the chassis 51 outside a location where the tape cassette 52 is to be charged, the capstan 70 being supported at its upper and lower ends by bearings 71, and attached to the cassis 51 such that it is inclined relative to the chassis at an angle substantially equal to those of the take-up side loading roller posts 60 and 61 at the loading terminal position. The inclined capstan 70 is brought into full contact with the magnetic tape 13 over its entire width which is introduced obliquely upwards from the take-up side loading roller post 61 along a sloped path and is inclined forwardly. During completion of the tape loading operation, the capstan 70 is in press-contact with the pinch roller 62 which is moved from the position of the recess 57 of the tape cassette 52 so that the magnetic tape 63 is held between the capstan 70 and the pinch roller 62 to be driven. Incidentally, the pinch roller 62 is arranged to have the same inclination angle as that of the capstan 70 in order to be in full contact with the capstan 70 over the entire width of the tape. Denoted by 72 is an audio-control head provided at a location in the vicinity of the capstan 70 between the take-up side second loading roller post 61 at the loading terminal position and the capstan 70. The audio-control head 72 is attached to the chassis 51 in such a manner that it is inclined at the same angle as that of the capstan 70 in order to facilitate contact between the audio-control head 72 and the magnetic tape 63, which is inclined forwards and introduced obliquely upwards along the sloped path from the take-up side second loading roller post 61 to the capstan 70. Denoted by 73 is an auxiliary roller post which moves in interlock with the pinch roller 12 such that it is relatively positioned in the recess 57 of the tape cassette 52 before starting the tape loading operation, and it moves together with the pinch roller 62 during completion of the tape loading operation, thereby guiding the magnetic tape 63 travelling between the capstan 70 and the pinch roller 62 to lead to a fixed inclined post 74. As regards the magnetic tape 63 fed from the take-up side second loading roller post 61 through the capstan 70 and the auxiliary roller post 73 while maintaining the forwardly-inclined posture, torsion of the magnetic tape 63, generated when the tape travelling is converted from the sloped path into a horizontally running path is corrected by the inclined fixed post 74 which is slantingly attached to the chassis 51 before the magnetic tape 63 reaches the tape cassette 52, and is then wound around the take-up reel 54 of the tape cassette 52.
In the loading post driving device, as shown in FIG. 20, the boats 64 and 65 are provided with holes 78 and 79 through which the boats 64 and 65 are engaged with drive shafts 76 and 77, respectively. For smooth movement of the boats 64 and 65 in the vertical and lateral directions, the holes 78 and 79 are formed to be somewhat larger than diameters of the drive shafts 76 and 77. Therefore, the loading post becomes so unstable in positioning that it may incline undesirably. As means for preventing such an inclination, it is possible to provide a projection 80 on the take-up side boat 65 to support the drive shaft 77 over a larger height range, thereby increasing stability of the loading post 61, as illustrated in FIG. 20.
With regard to the supply side boat 64, however, since the inclined post 66 is slanted toward a location above the hole 78, it is impossible to provide as long a projection extending upwards as in the take-up side boat 65. In addition, because of the supply side loading post 58 being at a higher level relative to the drive shaft 76 at the loading terminal position, even if a short projection is provided on the boat 64, the drive shaft 76 could not engage with the projection, resulting in that the stability could not be enhanced and the loading post may incline toward the rotary head cylinder 69 as indicated by an arrow A in FIG. 20.
Thus, the above conventional arrangement has suffered from such a second problem to be solved that when the unstable unloading post inclines toward the rotary head cylinder, it may damage the rotary head cylinder or interfere with rotation thereof by possible contact between the two members.
A conventional loading post holding device will be next described with reference to the drawings.
FIG. 21 is an enlarged view, partly cross-sectioned, as viewed in a direction of an arrow B in FIG. 20. In FIG. 21, 117 denotes a roller holder member for holding the roller or post 61 through which a shaft 116 is inserted. 118 denotes a pipe press-fitted to the take-up side boat 65 with the end portion of the shaft 116 inserted into the pipe 118.
FIG. 22 is a view of a part of FIG. 21, partly cross-sectioned, as viewed in a direction of arrows C--C in FIG. 21. In FIG. 22, the shaft 116 is pressed against one side of the inner peripheral surface (a reference surface n) of the pipe 118 by the distal end of a screw 119 which is screwed into a threaded hole 120 provided at one end of the take-up side boat 65, so that the shaft 116 will not rotate. In order to surely press-fix the shaft 116 against the reference surface n by the distal end of the screw 119, the pipe 118 is extended downwards below the underside of the take-up side boat 65 to such a dimension h that a certain length of the shaft is left or protruded below the point where the shaft is pressed.
The operation of the conventional loading post holding device thus arranged will be explained below.
First, in an initial state where a tape cassette (not shown) is charged, the supply side boat 64 is on standby at its initial position (or hole position) and the take-up side boat 65 is on standby while being supported on a rest 68a, as indicated by phantom lines in FIG. 20. When a manual playback button (not shown) is pushed in that state, power is transmitted to the ring gear 85 by a drive means (not shown) so that, on the supply side, the supply side boat 64 is driven in a direction of an arrow b by the supply side drive shaft 76 (see FIG. 20). Likewise, on the take-up side, the take-up side boat 65 is driven in a direction of an arrow a through the take-up side drive shaft 77. When an operation of loading a magnetic tape is completed, the supply side boat 64 and the take-up side boat 65 move to respective positions indicated by solid lines where a projection 64a of the supply side boat 64 is in abutment against a lug 67a and a projection 65a of the take-up side boat 65 is in abutment against a lug 68a.
However, the above loading post holding device in the prior art has suffered from such a third problem that in order to reduce a thickness in a direction of height of magnetic recording/playback apparatus, the thickness of the take-up side boat 65 must be reduced because of the take-up side loading guide 68 being inclined obliquely downwards, but the take-up side boat 65 requires a certain extent of thickness for providing the threaded hole 120 into which the screw 119 is screwed to positively press-fix the shaft 116 against the reference surface n. In addition, positive press-fixing of the shaft 116 against the reference surface n also requires the pipe 118 to extend downwards below the take-up side boat 65 by the dimension h, making it difficult to considerably reduce the total height of the loading post holding device.
Furthermore, in a loading post driving device of conventional magnetic recording/playback apparatus, means for turnably holding a loading ring to drive a loading post is generally arranged by providing shafts at several locations and holding the loading ring between a plurality of rollers mounted on each of the shaft.
Such an arrangement will be explained below with reference to the drawings.
FIG. 23 shows a top plan view of a VTR body. Denoted by 121 is a cassette having a supply reel 122 and a take-up reel 123 both provided therein. Between the supply reel 122 and the take-up reel 123, a magnetic tape 124 is stretched through guide posts 125a, 125b and 126.
The cassette 121 is rested on a base plate 130 at a predetermined position, the supply reel 122 in the cassette 121 is fitted over a supply reel stand 131, and further the take-up reel 123 is fitted over a take-up reel stand 132. 182 denotes an eraser head, 183 a control head, 184 a motor for a capstan and so forth, 185 a capstan, 186 an idler, and 188 a plunger. I and II denote a pair of magnetic tape withdrawer units for withdrawing the magnetic tape 124 out of the cassette 121 and winding the same along the circumference of a rotary head cylinder 133 provided in an inclined position.
The description concerning an arrangement of the withdrawer unit I is given below.
FIG. 24 is a cross-sectional view of the withdrawer unit I.
In FIG. 24, 133 denotes a rotary head cylinder around which the magnetic tape 124 is to be wound, and 156 and 157 are loading rings having gears 159 and 160' formed along the outer peripheral edges thereof and disposed on the underside of the base plate 130, one above the other in a concentric relationship. The loading rings 156 and 157 are held in place by three pairs of rollers 158 such as 158a, 158b; 158c, 158d; and 158e, 158f respectively fitted over roller pins or shafts 161a, 161b and 161c extending downwards from the base plate 130 in such a manner as to be able to turn in directions opposite to each other. 140 denotes a loading post provided on a withdrawer unit base 134 which engages with the magnetic tape 124 to withdraw the magnetic tape 124 out of the cassette 121 and, after completion of a tape withdrawing operation, to serve as one guide post for defining a running path of the magnetic tape. 141 denotes a correction post base on which a correction post 142 is mounted with an inclination of a predetermined angle .theta..
Denoted by 139 is a guide slot for guiding sliding movement of the withdrawer unit which withdraws the magnetic tape 124 out of the cassette 121 and winds the same along the circumference of the rotary head cylinder 133 provided in an inclined position.
A stopper 145 is fixed onto the base plate 130 by a screw 150 with a shaft 149 serving as a guide. Since an attachment hole 151 has an elongated shape, the stopper 145 is turnable about the shaft 149 to some PG,15 extent in directions of arrows Y--Y'.
The withdrawer unit II is symmetrical to the withdrawer unit I and thus will not be described herein.
The operation of the loading post driving device thus arranged will be explained below.
When a playback button (not shown) is pushed, a loading motor (not shown) starts rotating, whereupon a spur gear (not shown) is rotated through a worm gear (not shown) connected with a loading motor, thereby rotating the loading ring 156 held in mesh with the spur gear.
The withdrawer unit base 134 engaging with the loading ring 156 slides along the guide slot 139 in a direction of an arrow X, whereas a withdrawer unit base 134' slides along a guide slot 139' in a direction of an arrow Y. At this time, the magnetic tape 124 exits the cassette 121 and is kept in engagement with the loading posts 140 and 140' and the correction posts 141 and 141'. The loading posts 140 and 140' move along the circumference of the rotary head cylinder 133 and come into engagement with V-shaped grooves 146 and 146' which serve as stopper portions of the stoppers 145 and 145', respectively.
Under the condition that the loading posts 140 and 140' abut against the V-shape grooves 146 and 146' of the respective stoppers, the loading motor (not shown) stops its rotation and the loading posts 140 and 140' remain stopped there without returning backward.
Then, a plunger 188 is actuated to make an idler 186 abut against a capstan 185 for running the magnetic tape 124.
Additionally, when a stop button (not shown) is pushed, the device comes into an unloading state where the loading posts 140 and 140' are returned to their original positions.
However, the above conventional arrangement has suffered from such a fourth problem that since the means for holding the loading rings 156 and 157 in a turnable manner is constituted by providing the roller pins at several locations and holding the loading rings one above the other by the rollers fitted over the roller pins serving as shafts, not only the number of parts used is increased but also the number of assembling steps.